550i top speed
11-17-2007, 07:16 AM
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11-17-2007, 03:31 PM
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Originally Posted by pennetta' post='495568' date='Nov 17 2007, 10:30 AM
You seem to have the other answers you requested; the maximum RPM is a function of component stretch and component float due to ricipricating mass, adding for a safety margin. The pistons accelerate towards the valves and the valves open towards the pistons. At the begining of the intake and and at the end of the exhaust strokes is when a problem can occur, the pistons are at TDC (top dead center) and in the closest proximity to the values. Because of the temporary deformation of the components at high RPM's, the pistons goe higher and the valves open further into the combustion chamber. Additionally, valves can stop fully closing because they start bouncing off of the valve seats and then get slammed futher into the combustion champer, this is called floating. Both of these conditions can cause the piston and valve components to collide resulting in permanent engine damage.
Probably the same as you describe but I think of valve float as the springs not being ?stiff? enough to close the valve at very high revs.
MB, I think the old 300SLR of the 50s, had a cam followers that both opened and closed the valves. I think it was called ?desmodromic?. These were very high rev engines ? perhaps around 10,000 rpms.
There may be some contemporary engines with this arrangement.
11-17-2007, 06:16 PM
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Originally Posted by sixcard' post='495756' date='Nov 17 2007, 07:31 PM
... I think of valve float as the springs not being ?stiff? enough to close the valve at very high revs.
...
...
11-18-2007, 08:23 AM
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Originally Posted by sixcard' post='495756' date='Nov 17 2007, 08:31 PM
Thanks for the info, Pennetta. Your description of the high speed deformation of valves, pistons and rods is fascinating.
Probably the same as you describe but I think of valve float as the springs not being ?stiff? enough to close the valve at very high revs.
MB, I think the old 300SLR of the 50s, had a cam followers that both opened and closed the valves. I think it was called ?desmodromic?. These were very high rev engines ? perhaps around 10,000 rpms.
There may be some contemporary engines with this arrangement.
Probably the same as you describe but I think of valve float as the springs not being ?stiff? enough to close the valve at very high revs.
MB, I think the old 300SLR of the 50s, had a cam followers that both opened and closed the valves. I think it was called ?desmodromic?. These were very high rev engines ? perhaps around 10,000 rpms.
There may be some contemporary engines with this arrangement.
11-18-2007, 08:55 AM
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Originally Posted by pennetta' post='495940' date='Nov 18 2007, 12:23 PM
It can be done. The Yamaha YZF-R6 sport bike revs to 16,000 Rpm utilizing spring technology and its under $10,000.
11-18-2007, 09:05 AM
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Originally Posted by dsm' post='495176' date='Nov 16 2007, 09:23 AM
hi guys. just wanted to ask: 1. whats the top speed without limiter. 2. How fast can the steptronic go in 2nd gear. 3. why is the rpm limited to 6.5.... ty in advance
Steve Dinan says 175 for a Dinan 550 w/380 hp. My guess OEM is about 170. 2) look it up on Road & Track (they list maximum speed next to the ratio) and 3) I'm guesing that you're inquiring why redline isn't higher like the M5's V-10....It has to do with a number of factors. The 4.8 (N52 I believe) is a series production engine developed and made by BMW for use in more than one model. It is a jack of all trades. Decent consumption, smooth cold start and idle, very good longevity and reliability (we hope) and exceptional low, mid and top end power. The M5's V10 is a very costly purpose built engine designed by the gurus in the Motorsport division for use in essentially one platform and for use with the SMG exclusively. It has noticably less low end grunt than the 550 (below 4000 rpms) and it gets seriously low milege despite displacing only another 200cc. The V10 can rev higher because its stroke (the distance the piston travels) is shorter than a "regular" engine of its size. Like a Ferrari 2.8 litre V-8, it has large pistons that don't travel that far up and down. The result is less low end torque, but the reward is high end horsepower. You also need strong enough engine components to withstand the higher rpms and the ability to get enough air into the engine at those high rpms. If you take anything away from my amateur response here, let it be that the V10 is not a better version of the V8. They are different in design and construction and they are intended to meet very different goals. So a limit higher than 6500 or 7000 on a standard BMW V8 would probably come at a price you wouldn't want to pay....
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11-18-2007, 10:40 AM
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Originally Posted by 550isport' post='495956' date='Nov 18 2007, 07:05 PM
Steve Dinan says 175 for a Dinan 550 w/380 hp. My guess OEM is about 170.
DRP
DRP
According to some German members, the 545i not remapped -but with the speedlimit removed- can achieve 285 kmh easily (177 mph) .
The E39 M5 (the same power as the 550i) did 293 kmh (182 mph) .
11-18-2007, 11:57 AM
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Originally Posted by AlexFW' post='495989' date='Nov 18 2007, 02:40 PM
According to some German members, the 545i not remapped -but with the speedlimit removed- can achieve 285 kmh easily (177 mph) .
The E39 M5 (the same power as the 550i) did 293 kmh (182 mph) .
The E39 M5 (the same power as the 550i) did 293 kmh (182 mph) .
11-18-2007, 04:52 PM
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Originally Posted by 550isport' post='495956' date='Nov 18 2007, 01:05 PM
I'm guesing that you're inquiring why redline isn't higher like the M5's V-10....It has to do with a number of factors.